Direct Observation of Group-V Dopant Substitutional Defects in CdTe Single Crystals

Area of Science:

• Materials Science
• Solid-State Physics
• Semiconductor Physics

Background:

• Point defect chemistry is crucial for material properties and device performance.
• Group-V dopants, like arsenic (As), are key acceptors in cadmium telluride (CdTe), influencing hole concentration.
• The precise local atomic structure of As dopants in CdTe remains unclear due to measurement challenges and theoretical discrepancies.

Purpose of the Study:

• To directly observe the local atomic structure of As dopants in CdTe single crystals.
• To investigate the site occupancy of As dopants (As on Cadmium site - As_Cd, and As on Tellurium site - As_Te).
• To provide new insights into point defect behavior in II-VI semiconductors.

Main Methods:

• Utilizing X-ray fluorescence holography (XFH) for direct 3D atomic visualization around the As dopant.
• Combining experimental XFH observations with theoretical first-principles calculations.
• Analyzing As dopant behavior in CdTe single crystals.

Main Results:

• Direct observation of As dopant substituting on both Cadmium (As_Cd) and Tellurium (As_Te) lattice sites in CdTe.
• Experimental confirmation of As_Cd, a site previously less discussed compared to the known shallow acceptor As_Te.
• Detailed visualization of the three-dimensional atomic configurations around As dopants.

Conclusions:

• The study clarifies the local atomic structure of As dopants in CdTe, identifying substitution on both As_Cd and As_Te sites.
• It highlights the significance of the As_Cd site, expanding the understanding of point defects in CdTe.
• The integration of XFH and first-principles studies offers a powerful approach for defect analysis in II-VI semiconductors.